1. Field of the Invention
This invention relates generally to data gathering systems and, in particular, to systems and related methods for simultaneously gathering data from multiple wireless communication networks.
2. Description of the Related Art
The basic structure and operation of wireless communication networks, including cellular, paging, wireless local loop, and satellite communication networks are well known. A typical cellular communication network essentially consists of a plurality of mobile subscriber units (MSUs), a plurality of cell sites with base station equipment, a plurality of base station controllers (BSCs), which may be associated with each base station, or may be centralized to provide control for a plurality of base stations, a mobile telephone switching office (MTSO or Mobile Switching Center (MSC)) and various local or networked databases which may include a home location register (HLR), visitor location register (VLR), authentication center (AuC) and equipment identity register (EIR).
A typical cellular communication network is characterized by the concepts of frequency reuse and handoff. In some cellular systems, a frequency is reused at many sites which are geographically separated from each other by a distance sufficient to ensure that the interference from other sites utilizing the same frequency is low enough to permit a quality signal from the primary serving site. Handoffs are the process of changing the serving site as a subscriber moves from the primary service area of one site to that of another.
Ordinarily, cellular systems are initially designed with a set of cell sites that provide partial overlapping RF coverage over a market area of interest. In order to provide increased capacity, additional cell sites are constructed between the initial cell sites. The coverage area of each cell site is reduced through a combination of antenna system design and transmitter power reduction in order to provide limited overlap of individual coverage areas while maintaining contiguous coverage. In some cellular systems, capacity within each cell is limited by the available spectrum and the number of frequency assignments that can be assigned for that cell without violating the interference constraints of the common air interface standard employed for the network. Capacity can also be reused through the use of “sectored” sites, in which a single site is equipped with antenna systems and transceivers to permit multiple cells to be created from a single site. A common sectoring approach utilizes three sectors per site, each providing primary coverage in a different 120°-wide sector around the site, while partially overlapping with the other two sectors. Common frequency reuse patterns range from a reuse pattern of twenty-one, in which the frequency assignments are reused over a pattern of seven tri-sectored sites in Frequency Division Multiple Access (FDMA) systems, to reuse patterns of one, in which the same frequency assignment is reused in every cell in Code Division Multiple Access (CDMA) systems.
There are various common air interface (CAI) standards that are used in the radio communications link between the MSU and the cell site. The earliest type in common use is known as Frequency Division Multiple Access (FDMA), in which each communications channel consists of a single narrowband carrier, generally employing analog frequency modulation. Digital systems generally provide multiple communications channels within a single frequency assignment. In Time Division Multiple Access (TDMA) systems, a carrier is modulated with a binary signal, with channels cyclically assigned to unique timeslots. The number of channels available for a carrier frequency assignment varies with the particular TDMA standard, typically ranging from three to eight with current full rate vocoders. Another type of digital modulation in common use, Code Division Multiple Access (CDMA), typically differentiates up to sixty-four spread spectrum modulation channels using orthoganal spreading codes within a single wideband frequency assignment.
Channels that are transmitted from the base stations and received by MSUs are known as forward channels, while those that are transmitted from the MSU and received by the base station are known as reverse channels. Channels are further differentiated by their function. Those that are generally used for signaling between the MSU and the base station are known as control channels, while those that are generally used to carry voice or data signals are known as traffic channels. Generally, some limited forms of signaling are available when a call is in progress on a traffic channel to permit control of the call in progress or to support system requirements such as handoffs.
In certain cellular systems, when an MSU is in an idle mode, it may select a forward control channel (FCC) to monitor for signaling information. If the MSU is required to transmit information to the base station, it will do so on a corresponding reverse control channel (RCC). The protocols for the various common air interfaces determine which FCC-RCC pair is to be used. FCCs are used to send two types of messages. Overhead messages provide information to all MSU units monitoring the channel, and may include system and cell site identifiers, and information regarding the system configuration (e.g. neighbor lists). The FCC also provides information for specific users, including pages and short data messages. Absent any means of determining which cell is being monitored by a particular MSU, such messages would need to be broadcast over all the FCCs of all cells within a network in order to ensure that the MSU receives the message. This is practical in smaller systems, but in systems with more than a few tens of thousands of subscribers, it is desirable to subdivide the network into location areas (LAs) in order to avoid exceeding the data throughput capacity of the FCC. Subscriber messages can then be broadcast through the FCC of all the cells in the LA in which the MSU is monitoring a FCC.
Cellular systems ordinarily use a process known as registration in order to determine which LA serves a MSU. Generally, when an MSU is first turned on, it will initially monitor the strongest available FCC. It will then register in accordance with information contained within the FCC overhead data. This is accomplished by exchanging prescribed messages, including the subscriber identity, over the FCC-RCC pair. The VLR stores the information regarding the most current LA is then stored in the system VLR and the MSU. If the MSU later determines that the LA identifier included in the FCC no longer matches the data it has stored, it will initiate a location update that will repeat the registration process with the new LA identifier. Re-registration may also occur in response to system requests. In systems in which LAs are utilized, subscriber messages are initially sent only to cells within the system which correspond to the LA information for the MSU that is stored in the VLR.
Generally, when a call is made to a registered MSU, the network sends a page from the base station to the MSU by broadcasting a paging message on the FCC of the cells within the LA. If received, the MSU responds by sending its identifying information once again to the network along with a message confirming that it received the page. The network then sends a traffic channel assignment to the MSU on the forward control channel.
Ordinarily, when an MSU originates a call, the MSU initiates a signaling sequence which includes its identity and the called number using the RCC that corresponds to the monitored FCC. After verifying that the MSU corresponds to a valid subscriber record, the MSU is assigned to a traffic channel and the MTSO completes the call to the called number.
For a given geographic area, there are typically several competing service providers operating wireless communication networks. Each will have certain licensed frequency assignments, or bands of licensed frequencies, that it is permitted to use within its network. Each will have a common air interface, generally an industry standard, but occasionally a proprietary system developed by a particular vendor and not subjected to an industry standards process.
In the past, equipment has been developed to test the operation of, and characterize the quality of, the individual networks. Test equipment has been developed that allow the simultaneous testing of multiple networks at a single location. When coupled with navigation and data recording and analysis capabilities, they permit characterizing the comparative quality of various networks over a given set of geographical points, one location at a time (generally referred to as a drive route, since the test equipment is ordinarily installed in a vehicle and driven throughout a market area.)
However, such equipment typically is limited to gathering information from the portions of the networks that are in the vicinity of the test equipment. In major cellular system market area, this may mean the equipment is limited to gathering information from a small subset of the active cells at any given moment in time. In addition, since a purpose of the equipment is to test the operation and the quality of the wireless communication networks, the data processing capabilities of such equipment generally are not designed to gather data to make market share, usage comparisons, or user profiles for the different wireless communication networks.
Current methods of gathering information about subjects such as market share, usage, and user profile data often have been limited to telephone surveys, generally conducted by telemarketing research firms. This type of information is critical to wireless communications operators, who may expend significant resources on advertising and promotions to attract customers and need metrics to judge the effectiveness of these expenditures. But the accuracy and reliability of such telephone surveys sometimes is limited as they provide only anecdotal data and may use an insufficient statistical sample. Furthermore, in some cases these methods result in unsolicited charges to wireless customers. As a result, there has been a need for more comprehensive data gathering systems and related methods for gathering marketing information about wireless communication networks.